PHP (PHP: Hypertext Preprocessor)

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PHP (PHP: Hypertext Preprocessor)

« on: November 02, 2009, 12:40:18 PM »

What is PHP?

* PHP stands for PHP: Hypertext Preprocessor
* PHP is a server-side scripting language, like ASP
* PHP scripts are executed on the server
* PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.)
* PHP is an open source software
* PHP is free to download and use

What is a PHP File?

* PHP files can contain text, HTML tags and scripts
* PHP files are returned to the browser as plain HTML
* PHP files have a file extension of ".php", ".php3", or ".phtml"

What is MySQL?

* MySQL is a database server
* MySQL is ideal for both small and large applications
* MySQL supports standard SQL
* MySQL compiles on a number of platforms
* MySQL is free to download and use

PHP + MySQL

* PHP combined with MySQL are cross-platform (you can develop in Windows and serve on a Unix platform)

Why PHP?

* PHP runs on different platforms (Windows, Linux, Unix, etc.)
* PHP is compatible with almost all servers used today (Apache, IIS, etc.)
* PHP is FREE to download from the official PHP resource: www.php.net
* PHP is easy to learn and runs efficiently on the server side

Where to Start?

To get access to a web server with PHP support, you can:

* Install Apache (or IIS) on your own server, install PHP, and MySQL
* Or find a web hosting plan with PHP and MySQL support

« Last Edit: November 02, 2009, 12:45:55 PM by admin »

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PHP (PHP: Hypertext Preprocessor)

« on: November 02, 2009, 12:40:18 PM »

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PHP Syntax

« Reply #1 on: November 02, 2009, 12:43:00 PM »

A PHP scripting block always starts with <?php and ends with ?>. A PHP scripting block can be placed anywhere in the document.

On servers with shorthand support enabled you can start a scripting block with <? and end with ?>.

<?php
?>

A PHP file normally contains HTML tags, just like an HTML file, and some PHP scripting code.

Below, we have an example of a simple PHP script which sends the text "Hello World" to the browser:

<html>
<body>

<?php
echo "Hello World";
?>

</body>
</html>

Each code line in PHP must end with a semicolon. The semicolon is a separator and is used to distinguish one set of instructions from another.

There are two basic statements to output text with PHP: echo and print. In the example above we have used the echo statement to output the text "Hello World".

Note: The file must have a .php extension. If the file has a .html extension, the PHP code will not be executed.

Comments in PHP
In PHP, we use // to make a single-line comment or /* and */ to make a large comment block.

<html>
<body>

<?php
//This is a comment

/*
This is
a comment
block
*/
?>

</body>
</html>

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Variables in PHP

« Reply #2 on: November 02, 2009, 12:44:52 PM »

Variables are used for storing a values, like text strings, numbers or arrays.

When a variable is declared, it can be used over and over again in your script.

All variables in PHP start with a $ sign symbol.

The correct way of declaring a variable in PHP:

$var_name = value;
New PHP programmers often forget the $ sign at the beginning of the variable. In that case it will not work.

Let's try creating a variable containing a string, and a variable containing a number:

<?php
$txt="Welcome";
$x=6;
?>

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« Reply #2 on: November 02, 2009, 12:44:52 PM »

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PHP is a Loosely Typed Language

« Reply #3 on: November 02, 2009, 12:46:33 PM »

In PHP, a variable does not need to be declared before adding a value to it.

In the example above, you see that you do not have to tell PHP which data type the variable is.

PHP automatically converts the variable to the correct data type, depending on its value.

In a strongly typed programming language, you have to declare (define) the type and name of the variable before using it.

In PHP, the variable is declared automatically when you use it.

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Naming Rules for Variables

« Reply #4 on: November 02, 2009, 12:47:37 PM »

* A variable name must start with a letter or an underscore "_"
* A variable name can only contain alpha-numeric characters and underscores (a-z, A-Z, 0-9, and _ )
* A variable name should not contain spaces. If a variable name is more than one word, it should be separated with an underscore ($its_me), or with capitalization ($itsMe)

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« Reply #4 on: November 02, 2009, 12:47:37 PM »

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String Variables in PHP

« Reply #5 on: November 02, 2009, 12:48:31 PM »

String variables are used for values that contains characters.

In this chapter we are going to look at the most common functions and operators used to manipulate strings in PHP.

After we create a string we can manipulate it. A string can be used directly in a function or it can be stored in a variable.

Below, the PHP script assigns the text "Hello World" to a string variable called $txt:

<?php
$txt="Hello World";
echo $txt;
?>

The output of the code above will be:

Hello World
Now, lets try to use some different functions and operators to manipulate the string.

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The Concatenation Operator

« Reply #6 on: November 02, 2009, 12:49:20 PM »

There is only one string operator in PHP.

The concatenation operator (.) is used to put two string values together.

To concatenate two string variables together, use the concatenation operator:

<?php
$txt1="Hello World!";
$txt2="What a nice day!";
echo $txt1 . " " . $txt2;
?>

The output of the code above will be:

Hello World! What a nice day!
If we look at the code above you see that we used the concatenation operator two times. This is because we had to insert a third string (a space character), to separate the two strings.

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« Reply #6 on: November 02, 2009, 12:49:20 PM »

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String Functions

« Reply #7 on: November 02, 2009, 12:50:28 PM »

PHP: indicates the earliest version of PHP that supports the function.

Function[/t]

Description[/t]

PHP[/t]

Returns a string with backslashes in front of the specified characters

4

Returns a string with backslashes in front of predefined characters

3

Converts a string of ASCII characters to hexadecimal values

3

Alias of rtrim()

3

Returns a character from a specified ASCII value

3

Splits a string into a series of smaller parts

3

convert_cyr_string()

Converts a string from one Cyrillic character-set to another

3

convert_uudecode()

Decodes a uuencoded string

5

convert_uuencode()

Encodes a string using the uuencode algorithm

5

Returns how many times an ASCII character occurs within a string and returns the information

4

Calculates a 32-bit CRC for a string

4

One-way string encryption (hashing)

3

Outputs strings

3

Breaks a string into an array

3

Writes a formatted string to a specified output stream

5

get_html_translation_table()

Returns the translation table used by htmlspecialchars() and htmlentities()

4

Converts Hebrew text to visual text

3

Converts Hebrew text to visual text and new lines (\n) into <br />

3

html_entity_decode()

Converts HTML entities to characters

4

Converts characters to HTML entities

3

htmlspecialchars_decode()

Converts some predefined HTML entities to characters

5

htmlspecialchars()

Converts some predefined characters to HTML entities

3

Returns a string from the elements of an array

3

Alias of implode()

3

Returns the Levenshtein distance between two strings

3

Returns locale numeric and monetary formatting information

4

Strips whitespace from the left side of a string

3

Calculates the MD5 hash of a string

3

Calculates the MD5 hash of a file

4

Calculates the metaphone key of a string

4

Returns a string formatted as a currency string

4

Returns specific local information

4

Inserts HTML line breaks in front of each newline in a string

3

number_format()

Formats a number with grouped thousands

3

Returns the ASCII value of the first character of a string

3

Parses a query string into variables

3

Outputs a string

3

Outputs a formatted string

3

quoted_printable_decode()

Decodes a quoted-printable string

3

Quotes meta characters

3

Strips whitespace from the right side of a string

3

Sets locale information

3

Calculates the SHA-1 hash of a string

4

Calculates the SHA-1 hash of a file

4

Calculates the similarity between two strings

3

Calculates the soundex key of a string

3

Writes a formatted string to a variable

3

Parses input from a string according to a format

4

Replaces some characters in a string (case-insensitive)

5

Pads a string to a new length

4

Repeats a string a specified number of times

4

Replaces some characters in a string (case-sensitive)

3

Performs the ROT13 encoding on a string

4

Randomly shuffles all characters in a string

4

Splits a string into an array

5

str_word_count()

Count the number of words in a string

4

Compares two strings (case-insensitive)

3

Finds the first occurrence of a string inside another string (alias of strstr())

3

Compares two strings (case-sensitive)

3

Locale based string comparison

4

Returns the number of characters found in a string before any part of some specified characters are found

3

Strips HTML and PHP tags from a string

3

stripcslashes()

Unquotes a string quoted with addcslashes()

4

Unquotes a string quoted with addslashes()

3

Returns the position of the first occurrence of a string inside another string (case-insensitive)

5

Finds the first occurrence of a string inside another string (case-insensitive)

3

Returns the length of a string

3

strnatcasecmp()

Compares two strings using a "natural order" algorithm (case-insensitive)

4

Compares two strings using a "natural order" algorithm (case-sensitive)

4

String comparison of the first n characters (case-insensitive)

4

String comparison of the first n characters (case-sensitive)

4

Searches a string for any of a set of characters

5

Returns the position of the first occurrence of a string inside another string (case-sensitive)

3

Finds the last occurrence of a string inside another string

3

Reverses a string

3

Finds the position of the last occurrence of a string inside another string (case-insensitive)

5

Finds the position of the last occurrence of a string inside another string (case-sensitive)

3

Returns the number of characters found in a string that contains only characters from a specified charlist

3

Finds the first occurrence of a string inside another string (case-sensitive)

3

Splits a string into smaller strings

3

Converts a string to lowercase letters

3

Converts a string to uppercase letters

3

Translates certain characters in a string

3

Returns a part of a string

3

substr_compare()

Compares two strings from a specified start position (binary safe and optionally case-sensitive)

5

Counts the number of times a substring occurs in a string

4

substr_replace()

Replaces a part of a string with another string

4

Strips whitespace from both sides of a string

3

Converts the first character of a string to uppercase

3

Converts the first character of each word in a string to uppercase

3

Writes a formatted string to a specified output stream

5

Outputs a formatted string

4

Writes a formatted string to a variable

4

Wraps a string to a given number of characters

4

PHP String Constants PHP: indicates the earliest version of PHP that supports the constant.

Constant[/t]

Description[/t]

PHP[/t]

CRYPT_SALT_LENGTH

Contains the length of the default encryption method for the
system. For standard DES encryption, the length is 2

CRYPT_STD_DES

Set to 1 if the standard DES-based encryption with a 2 character salt is supported, 0 otherwise

CRYPT_EXT_DES

Set to 1 if the extended DES-based encryption with a 9 character salt is supported, 0 otherwise

CRYPT_MD5

Set to 1 if the MD5 encryption with a 12 character salt starting with $1$ is supported, 0 otherwise

CRYPT_BLOWFISH

Set to 1 if the Blowfish encryption with a 16 character salt starting with $2$ or $2a$ is supported, 0 otherwise0

HTML_SPECIALCHARS

HTML_ENTITIES

ENT_COMPAT

ENT_QUOTES

ENT_NOQUOTES

CHAR_MAX

LC_CTYPE

LC_NUMERIC

LC_TIME

LC_COLLATE

LC_MONETARY

LC_ALL

LC_MESSAGES

STR_PAD_LEFT

STR_PAD_RIGHT

STR_PAD_BOTH

[/hr][/td][/tr][/table][/td][/tr][/table][/td][/tr][/table][/td][/tr][/table][/td][/tr][/table][/td][/tr][/table]

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PHP Operators

« Reply #8 on: November 02, 2009, 12:51:48 PM »

This section lists the different operators used in PHP.
Arithmetic Operators

Operator[/t]

Description[/t]

Example[/t]

Result[/t]

+

Addition

x=2
x+2

4

-

Subtraction

x=2
5-x

3

*

Multiplication

x=4
x*5

20

/

Division

15/5
5/2

3
2.5

%

Modulus (division remainder)

5%2
10%8
10%2

1
2
0

++

Increment

x=5
x++

x=6

--

Decrement

x=5
x--

x=4

Assignment Operators

Operator[/t]

Example[/t]

Is The Same As[/t]

=

x=y

x=y

+=

x+=y

x=x+y

-=

x-=y

x=x-y

*=

x*=y

x=x*y

/=

x/=y

x=x/y

.=

x.=y

x=x.y

%=

x%=y

x=x%y

Comparison Operators

Operator[/t]

Description[/t]

Example[/t]

==

is equal to

5==8 returns false

!=

is not equal

5!=8 returns true

<>

is not equal

5<>8 returns true

>

is greater than

5>8 returns false

<

is less than

5<8 returns true

>=

is greater than or equal to

5>=8 returns false

<=

is less than or equal to

5<=8 returns true

Logical Operators

Operator[/t]

Description[/t]

Example[/t]

&&

and

x=6
y=3 (x < 10 && y > 1) returns true

||

or

x=6
y=3 (x==5 || y==5) returns false

!

not

x=6
y=3 !(x==y) returns true

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PHP If...Else Statements

« Reply #9 on: November 02, 2009, 12:56:27 PM »

Conditional statements are used to perform different actions based on different conditions.
Conditional Statements

Very often when you write code, you want to perform different actions for different decisions.

You can use conditional statements in your code to do this.

In PHP we have the following conditional statements:

* if statement - use this statement to execute some code only if a specified condition is true
* if...else statement - use this statement to execute some code if a condition is true and another code if the condition is false
* if...elseif....else statement - use this statement to select one of several blocks of code to be executed
* switch statement - use this statement to select one of many blocks of code to be executed

The if Statement

Use the if statement to execute some code only if a specified condition is true.
Syntax

if (condition) code to be executed if condition is true;
The following example will output "Have a nice weekend!" if the current day is Friday:

<html>
<body>

<?php
$d=date("D");
if ($d=="Fri") echo "Have a nice weekend!";
?>

</body>
</html>

Notice that there is no ..else.. in this syntax. You tell the browser to execute some code only if the specified condition is true.
The if...else Statement

Use the if....else statement to execute some code if a condition is true and another code if a condition is false.
Syntax

if (condition)
  code to be executed if condition is true;
else
  code to be executed if condition is false;

Example

The following example will output "Have a nice weekend!" if the current day is Friday, otherwise it will output "Have a nice day!":

<html>
<body>

<?php
$d=date("D");
if ($d=="Fri")
  echo "Have a nice weekend!";
else
  echo "Have a nice day!";
?>

</body>
</html>

If more than one line should be executed if a condition is true/false, the lines should be enclosed within curly braces:
<html>
<body>

<?php
$d=date("D");
if ($d=="Fri")
  {
  echo "Hello!<br />";
  echo "Have a nice weekend!";
  echo "See you on Monday!";
  }
?>

</body>
</html>

The if...elseif....else Statement

Use the if....elseif...else statement to select one of several blocks of code to be executed.
Syntax

if (condition)
  code to be executed if condition is true;
elseif (condition)
  code to be executed if condition is true;
else
  code to be executed if condition is false;

Example

The following example will output "Have a nice weekend!" if the current day is Friday, and "Have a nice Sunday!" if the current day is Sunday. Otherwise it will output "Have a nice day!":

<html>
<body>

<?php
$d=date("D");
if ($d=="Fri")
  echo "Have a nice weekend!";
elseif ($d=="Sun")
  echo "Have a nice Sunday!";
else
  echo "Have a nice day!";
?>

</body>
</html>

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PHP Switch Statement

« Reply #10 on: November 02, 2009, 12:59:48 PM »

The PHP Switch Statement

Use the switch statement to select one of many blocks of code to be executed.
Syntax

switch (n)
{
case label1:
  code to be executed if n=label1;
  break;
case label2:
  code to be executed if n=label2;
  break;
default:
  code to be executed if n is different from both label1 and label2;
}

This is how it works: First we have a single expression n (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed. Use break to prevent the code from running into the next case automatically. The default statement is used if no match is found.
Example

<html>
<body>

<?php
switch ($x)
{
case 1:
  echo "Number 1";
  break;
case 2:
  echo "Number 2";
  break;
case 3:
  echo "Number 3";
  break;
default:
  echo "No number between 1 and 3";
}
?>

</body>
</html>

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PHP Arrays

« Reply #11 on: November 02, 2009, 01:02:08 PM »

What is an Array?

A variable is a storage area holding a number or text. The problem is, a variable will hold only one value.

An array is a special variable, which can store multiple values in one single variable.

If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:

$cars1="Saab";
$cars2="Volvo";
$cars3="BMW";

However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?

The best solution here is to use an array!

An array can hold all your variable values under a single name. And you can access the values by referring to the array name.

Each element in the array has its own index so that it can be easily accessed.

In PHP, there are three kind of arrays:

* Numeric array - An array with a numeric index
* Associative array - An array where each ID key is associated with a value
* Multidimensional array - An array containing one or more arrays

Numeric Arrays

A numeric array stores each array element with a numeric index.

There are two methods to create a numeric array.

1. In the following example the index are automatically assigned (the index starts at 0):

$cars=array("Saab","Volvo","BMW","Toyota");
2. In the following example we assign the index manually:

$cars[0]="Saab";
$cars[1]="Volvo";
$cars[2]="BMW";
$cars[3]="Toyota";

Example

In the following example you access the variable values by referring to the array name and index:

<?php
$cars[0]="Saab";
$cars[1]="Volvo";
$cars[2]="BMW";
$cars[3]="Toyota";
echo $cars[0] . " and " . $cars[1] . " are Swedish cars.";
?>

The code above will output:

Saab and Volvo are Swedish cars.
Associative Arrays

An associative array, each ID key is associated with a value.

When storing data about specific named values, a numerical array is not always the best way to do it.

With associative arrays we can use the values as keys and assign values to them.
Example 1

In this example we use an array to assign ages to the different persons:

$ages = array("Peter"=>32, "Quagmire"=>30, "Joe"=>34);Example 2

This example is the same as example 1, but shows a different way of creating the array:

$ages['Peter'] = "32";
$ages['Quagmire'] = "30";
$ages['Joe'] = "34";

The ID keys can be used in a script:

<?php
$ages['Peter'] = "32";
$ages['Quagmire'] = "30";
$ages['Joe'] = "34";

echo "Peter is " . $ages['Peter'] . " years old.";
?>

The code above will output:

Peter is 32 years old.
Multidimensional Arrays

In a multidimensional array, each element in the main array can also be an array. And each element in the sub-array can be an array, and so on.
Example

In this example we create a multidimensional array, with automatically assigned ID keys:

$families = array
  (
  "Griffin"=>array
  (
  "Peter",
  "Lois",
  "Megan"
  ),
  "Quagmire"=>array
  (
  "Glenn"
  ),
  "Brown"=>array
  (
  "Cleveland",
  "Loretta",
  "Junior"
  )
  );

The array above would look like this if written to the output:

Array
(
[Griffin] => Array
  (
  [0] => Peter
  [1] => Lois
  [2] => Megan
  )
[Quagmire] => Array
  (
  [0] => Glenn
  )
[Brown] => Array
  (
  [0] => Cleveland
  [1] => Loretta
  [2] => Junior
  )
)

Example 2

Lets try displaying a single value from the array above:

echo "Is " . $families['Griffin'][2] .
" a part of the Griffin family?";

The code above will output:

Is Megan a part of the Griffin family?

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PHP Looping - While Loops

« Reply #12 on: November 02, 2009, 01:04:18 PM »

Loops execute a block of code a specified number of times, or while a specified condition is true.

PHP Loops

Often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal lines in a script we can use loops to perform a task like this.

In PHP, we have the following looping statements:

* while - loops through a block of code while a specified condition is true
* do...while - loops through a block of code once, and then repeats the loop as long as a specified condition is true
* for - loops through a block of code a specified number of times
* foreach - loops through a block of code for each element in an array

The while Loop

The while loop executes a block of code while a condition is true.
Syntax

while (condition)
  {
  code to be executed;
  }

Example

The example below defines a loop that starts with i=1. The loop will continue to run as long as i is less than, or equal to 5. i will increase by 1 each time the loop runs:

<html>
<body>

<?php
$i=1;
while($i<=5)
  {
  echo "The number is " . $i . "<br />";
  $i++;
  }
?>

</body>
</html>

Output:

The number is 1
The number is 2
The number is 3
The number is 4
The number is 5

The do...while Statement

The do...while statement will always execute the block of code once, it will then check the condition, and repeat the loop while the condition is true.
Syntax

do
  {
  code to be executed;
  }
while (condition);

Example

The example below defines a loop that starts with i=1. It will then increment i with 1, and write some output. Then the condition is checked, and the loop will continue to run as long as i is less than, or equal to 5:

<html>
<body>

<?php
$i=1;
do
  {
  $i++;
  echo "The number is " . $i . "<br />";
  }
while ($i<=5);
?>

</body>
</html>

Output:

The number is 2
The number is 3
The number is 4
The number is 5
The number is 6

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Re: PHP (PHP: Hypertext Preprocessor)

« Reply #13 on: November 02, 2009, 01:05:44 PM »

The for Loop

The for loop is used when you know in advance how many times the script should run.
Syntax

for (init; condition; increment)
  {
  code to be executed;
  }

Parameters:

* init: Mostly used to set a counter (but can be any code to be executed once at the beginning of the loop)
* condition: Evaluated for each loop iteration. If it evaluates to TRUE, the loop continues. If it evaluates to FALSE, the loop ends.
* increment: Mostly used to increment a counter (but can be any code to be executed at the end of the loop)

Note: Each of the parameters above can be empty, or have multiple expressions (separated by commas).
Example

The example below defines a loop that starts with i=1. The loop will continue to run as long as i is less than, or equal to 5. i will increase by 1 each time the loop runs:

<html>
<body>

<?php
for ($i=1; $i<=5; $i++)
  {
  echo "The number is " . $i . "<br />";
  }
?>

</body>
</html>

Output:

The number is 1
The number is 2
The number is 3
The number is 4
The number is 5

The foreach Loop

The foreach loop is used to loop through arrays.
Syntax

foreach ($array as $value)
  {
  code to be executed;
  }

For every loop iteration, the value of the current array element is assigned to $value (and the array pointer is moved by one) - so on the next loop iteration, you'll be looking at the next array value.
Example

The following example demonstrates a loop that will print the values of the given array:

<html>
<body>

<?php
$x=array("one","two","three");
foreach ($x as $value)
  {
  echo $value . "<br />";
  }
?>

</body>
</html>

Output:

one
two
three

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